Spray gun system for slurry

ABSTRACT

A spray gun for liquid slurry of the type using atomized air as the propellant medium, particularly a four-way valve system for said gun enabling selective spray of solvent or slurry while continuously flowing solvent and slurry through closed circulation systems. The continuous flowing of solvent through the gun and absent the slurry enables a clean flushing of the gun and eliminates slurry buildup in the gun inner chambers and nozzle.

States Patent [4 1 Jan. 25, 1972 [54] SPRAY GUN SYSTEM FOR SLURRY [72]Inventor: Hendrik F. Bok, 52 Thompson Street,

Fairhaven, Mass.

[73] Assignee: EPEC Systems Corporation, New Bedford,

Mass.

[22] Filed: Mar. 11, 1970 211 Appl. No.: 18,458

[51] Int. Cl .3051) 9/00 [58] Field of Search ..239/124127; 222/148,318; 137/240, 563, 599.1

[56] References Cited UNITED STATES PATENTS 3,219,273 11/1965 Killen137/240 X 3,334,648 8/1967 Probst ..137/240 X 3,373,762 3/1968 Korchak..137/240 3,443,578 5/1968 Hedin ..137/240 Primary Examiner-M. HensonWood, Jr. Assistant ExaminerEdwin D. Grant Attorney-David H. Semmes 57ABSTRACT 9 Claims, 6 Drawing Figures we wrap me ran /WW Awmr/m l i lPATENTED m2 5 1912- ATTORNEY PATENTEDJMSW 31637,].36 MM M HF 4 INVENTORBY awe/21M ATTORNEY sat GIJN SYSTEM ron swam BACKGROUND OF THE INVENTIONIn general, the spray application of slurry solutions, such as waterorsolvent-based glass frit, solder glass, phosphor and other fastsettling, nonsoluble materials, is difficult if such applications are tobe of low output, consistent in solid percentage and repeatable.

Spray guns are available which have a material inlet and an outlet atthe spray gun head, allowing a constant flow of slurry through the gunhead to prevent settling of the heavy solids in hoses, gun head andnozzle.

However, conventional spray guns utilize a needle to close the orificeof the nozzle, as spraying is to be terminated. This needle-nozzlecombination is the source of some of the problems encountered byspraying slurries. The cavity, formed by the needle seat, cannot bereadily flushed by the slurry which circulates through the gun head,particularly if the nozzle is pointed downwardly. The high-weight solidssettle in the nozzle tip, causing a severe restriction when the needleis pulled back for spraying. Since most slurries are of an abrasivenature, the needle-nozzle seats are subject to heavy wear, principallybecause there is always a misalignment of the needle in relationship tothe center of the nozzle. This causes wear on one side of the seat,rendering the nozzle and needle useless in a very short time.

The object of this invention is to provide an automatic spray gun forspraying the above-mentioned slurries in applications where precision,cleanliness and repeatability is required. The automatic spray gun headconsists basically of two four-way valves, double stacked in one housingwith an outlet opening which is placed just above the nozzle. Thiscombined valve gun-head arrangement is mounted via a support tubing by alinear guide system and connected to a drive mechanism. Inside thesupport tubing is placed a drive mechanism for actuating the four-wayvalves.

SUMMARY OF THE INVENTION According to the present invention separateslurry circulation conduits and solvent circulation conduits aremaintained so that either or both slurry and solvent maybe continuouslycirculated through the spray gun. As the slurry spraying is completed,the slurry circulation circuit may be short circuited and solvent may becirculated continuously through the spray gun by opening a solvent valvein the solvent circulation circuit, so as to flush out the gun and leavethe gun ready for respraying of slurry. As the gun is shut down fromsolvent or slurry spraying, only the slurry is continuously circulated,the solvent valve has closed the solvent circuit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. IA is a schematic view of thespray gun system in nospray attitude;

FIG. IB is a schematic view of the system in slurry spray attitude;

FIG. IC is a schematic showing the system in a solvent spray, flushingattitude; 4

FIG. 2 is a vertical section of a proposed spray gun and fourway valve;

FIG. 3 is an end elevation of the four-way valve; and

FIG. 4 is a side elevation of the proposed gun together with areciprocating mechanism positioned in a spray chamber.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I shows a flow diagram ofa slurry and solvent-clean circulation system with a double-stackedslurry/solvent selector four-way valve as a control device operative tooff" and on positions for selective slurry/solvent flow-through spraygun head I2.

FIG. 1A shows the gun 12 in the no-spray condition. The slurryconstantly circulates from the slurry container 14 via circulation pumpI6, supply hose 18 to the upper stacked four-way valve inlet port A,through rotor passage 20 to the exit port D, via flow canal 22, drilledin the body of the double stacked four-way valve, to the inlet port DIof the lower stacked valve 24 and via rotor passage to the exit port Al,then back to the slurry container via conduit 26. The solvent cleaningsolution is short circuited by the double solenoid valve 28 serving as asolvent otF control. Neither the solvent cleaning solution nor theslurry will flow through the spray gun head.

FIG. IB shows the gun in the slurry spray condition. The double-stackedfour-way valve 10 is activated and the rotor 20 connects the ports A andports B and also ports CI and D1. The slurry now circulates through gunhead 12, and because the nozzle orifice 30 is open at all times, thespraying of the slurry will commence. The solenoid valve 28 is opened atthe same time when the double-stacked valve is activated and cleaningsolution is now circulating via the ports C and D. This will prevent anyclogging of the slurry left in the passage. The solids, picked up by thecleaning solution, will be carried to the cleaning solution container32, and since the suction fitting 34 at the bottom is raised, the solidsare allowed to settle on the bottom for easy recovery.

FIG. IC shows the gun-off condition after the spray is terminated. Thedouble-stacked four-way valve 10 is again placed in the position wherethe rotor 20 connects the ports A and D and ports DI and AI, causing theslurry to circulate through the valve itself. After the slurry stopsflowing through the gun, the cleaning solution is, for a short period oftime, allowed to flush through the gun and will remove all slurryresidue by circulation and actually spraying.

After the above-mentioned slurry residue has been removed from the spraygun head, solenoid valve 28 is deactivated and the condition asdescribed with FIG. IA is restored.

Any time the slurry spray is activated, the gun will cycle in a sequenceas shown in FIG. IB, IC and IA.

FIG. 2 shows a cross section of the double-stacked four-way valve. Theoutlet ports B and BI are combined in the valve housing to form onesingle outlet 48, which terminates in the spray gun head, just above thenozzle. The stainless steel rotor 20 rotates through in teflon sleeve 31with a guide 60 therein. Rotation of rotor 20 is accomplished within thesupport tubing 35 by means rotor actuator shaft 72.

Solvent and slurry inlet and outlet ducts are generally indicated at 58,59, 68. The gun body includes a closure cap 54 with spring 56 biassingrotor 20 to operative position. Spray adjustment and assembly mechanismincludes boss 64 and fins 66, as shown in FIG. 4.

FIG. 3 shows the top view of the double-stacked four-way valve. The portinlets ABC form the top four-way valve, the port inlets A B', C form thelower four-way valve.

FIG. 4 illustrates the automatic spray gun placed in a typical spraychamber I03 used for precision coating of small ceramic substrates 3h,placed on a vacuum plate 40 and conveyed through the slots 42 of thespray chamber. The spray gun head is propelled in a reciprocation motionby air cylinder 44, via double guide rail 46, I8 and roller bushings 50.

A rotary actuator 52 is shown on top of the support tubing 35 and isused to activate the rotor 2'0 of the double-stacked four-way valvethrough a 90 rotation through shafting supported by bearings III, 62 andgearing 7A, 75.

In FIG. 4 the gun is shown together with a reciprocating apparatusplaced within a spray booth of the type having a plurality of staggeredbattles IIM at its discharge end I10 with individual spray nozzles 106communicant with each bafi'le so as to spray solvent on the baffles, acollecting pan beneath the spray area and a laminar flow clean airsource II2 at the end of the spray booth opposite the wettedl bafiles.

I claim:

I. A spray gun system for air-pressurized spraying of slurry comprising:

A. a source of slurry and a continuous slurry circulation conduit forsaid slurry;

B. a spray gun with discharge nozzle mounted in said circulation conduitand having:

i. a slurry/solvent selector valve communicant with said circulationconduit;

ii. an air atomization conduit communicant with said nozzle in saidspray gun;

C. a source of solvent having:

i. a continuous solvent circulation conduit for said solvent communicantwith said selector valve and;

D. means driving said selector valve to off and on positions, said onposition charging said gun through said circulation conduit with liquidslurry and solvent.

2. A spray gun circulation system as in claim 1, said solventcirculation conduit including a solenoid solvent off valve.

3. A spray gun system for slurry as in claim 1, said spray gun having adouble-stacked four-way valve for interconnection with solvent/slurryconduits selectively.

4. A spray gun system for slurry as in claim 3, said four-way valvebeing operable to a no-spray off position, while circulating solventthrough said spray gun.

5. A spray gun system for solvent as in claim 4, said fourway valve inno-spray otf" position admitting continuous flow of slurry through aportion of said solvent conduit and back into said source of slurry.

6. A spray gun system for slurry as in claim 5, said valve in solventspray position permitting a continuous flow of solvent through said gunand back into said source of solvent, while continuously circulatingslurry through a portion of said slurry circulation conduit.

7. A spray gun system for slurry as in claim 6, including meansagitating said source of slurry continuously.

8. A spray gun system for slurry as in claim 7, including independentpump means positioned in said solvent circulation conduit and saidslurry circulation conduit.

9. A spray gun system for slurry as in claim 4, said four-way beingcapable of permitting spraying of solvent only through said gun, asslurry is circulated through a portion of said slurry circulationconduit.

l l l

1. A spray gun system for air-pressurized spraying of slurry comprising:A. a source of slurry and a continuous slurry circulation conduit forsaid slurry; B. a spray gun with discharge nozzle mounted in saidcirculation conduit and having: i. a slurry/solvent selector valvecommunicant with said circulation conduit; ii. an air atomizationconduit communicant with said nozzle in said spray gun; C. a source ofsolvent having: i. a continuous solvent circulation conduit for saidsolvent communicant with said selector valve and; D. means driving saidselector valve to ''''off'''' and ''''on'''' positions, said ''''on''''position charging said gun through said circulation conduit with liquidslurry and solvent.
 2. A spray gun circulation system as in claim 1,said solvent circulation conduit including a solenoid solvent''''off'''' valve.
 3. A spray gun system for slurry as in claim 1, saidspray gun having a double-stacked four-way valve for interconnectionwith solvent/slurry conduits selectively.
 4. A spray gun system forslurry as in claim 3, said four-way valve being operable to a no-spray''''off'''' position, while circulating solvent through said spray gun.5. A spray gun system for solvent as in claim 4, said four-way valve inno-spray ''''off'''' position admitting continuous flow of slurrythrough a portion of said solvent conduit and back into said source ofslurry.
 6. A spray gun system for slurry as in claim 5, said valve insolvent spray position permitting a continuous flow of solvent throughsaid gun and back into said source of solvent, while continuouslycirculating slurry through a portion of said slurry circulation conduit.7. A spray gun system for slurry as in claim 6, including meansagitating said source of slurry continuously.
 8. A spray gun system forslurry as in claim 7, including independent pump means positioned insaid solvent circulation conduit and said slurry circulation conduit. 9.A spray gun system for slurry as in claim 4, said four-way valve beingcapable of permitting spraying of solvent only through said gun, asslurry is circulated through a portion of said slurry circulationconduit.